# IGES vs Parasolid: Surfaces, Solids and CAD Exchange

Compare IGES and Parasolid X_T by the receiving system, solid closure and units. Neither extension guarantees a perfect transfer or a native feature tree.

This guide covers general CAD workflows. CADProps supports STEP, IGES, SolidWorks parts and ZIP assemblies, STL, OBJ, 3MF and static GLB/GLTF. Validated conversions are downloadable. Partial assemblies carry warnings; properties cover loaded geometry only.

IGES and Parasolid both move 3D geometry between CAD systems, but they are not interchangeable promises. IGES is an older neutral exchange format often associated with curves and surfaces. Parasolid exchange, commonly a text `.x_t` file, is kernel geometry used by several mechanical CAD applications. The useful choice is the one the receiving system has actually been tested with.

CADProps can inspect readable IGES and text Parasolid X_T, and can write STEP from supported IGES or X_T geometry. Binary Parasolid X_B is not enabled. Renaming `.x_b` to `.x_t`, or `.igs` to `.x_t`, does not translate the file.

## What each file is for

| Question | IGES | Parasolid X_T |
|---|---|---|
| Typical role | Neutral curve and surface exchange, including legacy workflows | Kernel solid and surface data for Parasolid-based systems |
| Common extensions | `.iges`, `.igs` | `.x_t` for text; `.x_b` is binary and not enabled here |
| Closed-solid volume | Only when the imported geometry is a valid closed solid | Only for readable solid geometry that meets the same closure rules |
| Open surfaces | Area and dimensions can still be available | A shaded surface is not proof of a solid |
| Feature history | Not preserved as native features | Not preserved as native features |
| Best default for an unknown recipient | Only if that recipient qualified IGES | Only if that recipient uses a Parasolid path |

NIST's STEP resources describe the broader neutral product-model role of STEP when neither IGES nor Parasolid is the agreed path. See the [NIST STEP File Analyzer and Viewer](https://www.nist.gov/services-resources/software/step-file-analyzer-and-viewer). [Parasolid vs STEP](https://www.cadprops.com/guides/parasolid-vs-step/index.md) and [STEP vs IGES](https://www.cadprops.com/guides/step-vs-iges/index.md) cover those separate choices.

## Do not treat "IGES is surfaces" as the whole comparison

An IGES file can import as useful geometry, including solids when the translator sews or writes them. A Parasolid file can also arrive as surfaces, an incomplete body or a version the reader rejects. A shaded preview does not prove a manufacturing solid.

Ask:

- Did the intended faces and bodies arrive?
- Is the geometry closed where a volume is required?
- Are the units confirmed by one known dimension?
- Does the recipient need assembly structure, names or only the shape?
- Which export version did the sender actually write?

Open CASCADE's property routines depend on closure and consistent orientation and do not check every precondition automatically. [BRepGProp documentation](https://dev.opencascade.org/doc/refman/html/class_b_rep_g_prop.html). If volume is unavailable, report that state. Do not substitute a bounding-box product or a zero.

## When Parasolid is the stronger handoff

Use X_T when both sides already share a tested Parasolid path: the same kernel family, a known schema version and a recipient who asked for it. That can preserve precise solids without an extra neutral translation.

It is still an exchange file. Sketches, constraints and the authoring feature tree are not a portable promise. If the job needs the original Solid Edge, NX or other native history, keep that native model. X_T is not a substitute for it.

On this site, open the file in the [Parasolid viewer](https://www.cadprops.com/tools/parasolid-viewer/index.md) and use [Parasolid to STEP](https://www.cadprops.com/tools/parasolid-to-step/index.md) only when the next system wants STEP. Recheck one known dimension, the body count and a critical face after conversion.

## When IGES is still the right request

Keep IGES when a legacy process, a surface workflow or a qualified importer expects it. Do not convert a working IGES path to Parasolid only because Parasolid sounds more modern.

Readable IGES can report dimensions and surface area even when a closed-solid volume is unavailable. The [IGES surfaces guide](https://www.cadprops.com/guides/iges-surfaces-not-solid/index.md) explains that result. [IGES to STEP](https://www.cadprops.com/tools/iges-to-step/index.md) is a separate, validated direction. It does not reconstruct a feature tree, and it cannot invent solids that were never closed.

## A receiving check for either file

1. Keep the original attachment unchanged.
2. Confirm the extension matches the bytes: IGES is not X_T, and X_B is not enabled.
3. Open it in the [IGES viewer](https://www.cadprops.com/tools/iges-viewer/index.md) or the Parasolid viewer, depending on the file you actually received.
4. Verify one known linear dimension before using area, volume or mass.
5. Treat missing volume as unavailable, not as zero.
6. If you convert to STEP, validate the STEP in the system that will use it.

Mass is volume times a density you supply. A filename or a color does not certify the material. Assemblies that load only some components must stay marked incomplete.

## Related reading

- [IGES Surfaces Not Solid? Check Volume and Open Shells](https://www.cadprops.com/guides/iges-surfaces-not-solid/index.md)
- [Open a Solid Edge File Without Solid Edge](https://www.cadprops.com/guides/open-solid-edge-without-solid-edge/index.md)
- [How to Open an X_T File Online Without Parasolid Software](https://www.cadprops.com/guides/open-x-t-file-online/index.md)
- [Parasolid vs STEP: CAD Geometry and Exchange Formats](https://www.cadprops.com/guides/parasolid-vs-step/index.md)
- [SAT vs IGES: ACIS Solids or Neutral CAD Surfaces](https://www.cadprops.com/guides/sat-vs-iges/index.md)
- [STEP vs IGES: Which CAD Exchange Format Fits the Job?](https://www.cadprops.com/guides/step-vs-iges/index.md)
- [What B-Rep Means in a STEP or IGES File](https://www.cadprops.com/guides/what-is-brep/index.md)

Original article: https://www.cadprops.com/guides/iges-vs-parasolid/

HTML page: https://www.cadprops.com/guides/iges-vs-parasolid/